Your guess that it's possible that such a kind of TLD means the expiration date doesn't matter is correct. (Neustar calls them .US locality domain names.) I just inquired about a different .us domain myself and got this response from Neustar support:

=
Although the whois record may show a system generated expiration date, .US locality domains do not expire and are automatically renewed. At this time, there is no charge for locality domains, so there is no action needed on your part to ensure the registration is active. Additionally, in the WHOIS record, the status autoRenewPeriod is listed to indicate that your domain has been auto renewed by the Registry. This status and the domain's expiration date will remain the same until 45 days after your expiration date which is when your domain's expiration date will extend by 1 year from the date and the autoRenewPeriod status is removed from WHOIS.
=

Note that this only applies to .US /locality/ domain names, not all .us domain names. You can read more about the difference under the ".US Locality Management" section at
https://www.about.us/faqs

-- 
Lee Knutson, CISSP
Network Systems Specialist
Minnesota State
30 East 7th Street, St. Paul, MN 55101
[log in to unmask]
Desk: 651-201-1609


-----Original Message-----
From: MICE Discuss <[log in to unmask]> On Behalf Of Frank Bulk
Sent: Sunday, February 7, 2021 8:31 AM
To: [log in to unmask]
Subject: [MICE-DISCUSS] state.mn.us expired yesterday?

It appears that state.mn.us expired yesterday?  It's possible with such kind of TLD that that doesn't matter?

Frank Bulk

Registry WHOIS Server : whois.nic.us
Domain Name: state.mn.us
Registry Domain ID: D3624286-US
Registrar WHOIS Server:
Registrar URL: https://nam02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.whois.us%2F&amp;data=04%7C01%7Clee.knutson%40MINNSTATE.EDU%7C74faa8d0779d41a3ab7e08d8cb7516ea%7C5011c7c60ab446ab9ef4fae74a921a7f%7C0%7C0%7C637483051048582374%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=YX3kvd976ts5qk%2FE4FdEdggsMaWq4vvq%2F1zcSEiV4nI%3D&amp;reserved=0
Updated Date: 2021-01-12T14:03:55Z
Creation Date: 2003-02-06T20:25:14Z
Registry Expiry Date: 2021-02-06T20:25:14Z
Registrar: State of Minnesota
Registrar IANA ID:
Registrar Abuse Contact Email:
Registrar Abuse Contact Phone:
Domain Status: ok https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Ficann.org%2Fepp%23ok&amp;data=04%7C01%7Clee.knutson%40MINNSTATE.EDU%7C74faa8d0779d41a3ab7e08d8cb7516ea%7C5011c7c60ab446ab9ef4fae74a921a7f%7C0%7C0%7C637483051048582374%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=DUbJXsjgp6k2T30KDDzOWQI8RCdPITDNxGb77Zz%2FeT4%3D&amp;reserved=0
Domain Status: autoRenewPeriod https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Ficann.org%2Fepp%23autoRenewPeriod&amp;data=04%7C01%7Clee.knutson%40MINNSTATE.EDU%7C74faa8d0779d41a3ab7e08d8cb7516ea%7C5011c7c60ab446ab9ef4fae74a921a7f%7C0%7C0%7C637483051048582374%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=t812p1fPJvOtP0ehLADbEI72Ki1KZJsYdKX2ltsB05k%3D&amp;reserved=0
Registry Registrant ID: C7705028-US
Registrant Name: Network Operations Center Registrant Organization: State of Minnesota Registrant Street: Office of Enterprise Technology Registrant Street: 500 Centennial Office Building Registrant Street: 658 Cedar Street Registrant City: St. Paul Registrant State/Province: MN Registrant Postal Code: 55155 Registrant Country: US Registrant Phone: +1.6512971111 Registrant Phone Ext:
Registrant Fax: +1.6512975368
Registrant Fax Ext:
Registrant Email: nic<%>nic.state.mn.us
Registrant Application Purpose: P5
Registrant Nexus Category: C21
Registry Admin ID: C7705028-US
Admin Name: Network Operations Center
Admin Organization: State of Minnesota
Admin Street: Office of Enterprise Technology Admin Street: 500 Centennial Office Building Admin Street: 658 Cedar Street Admin City: St. Paul Admin State/Province: MN Admin Postal Code: 55155 Admin Country: US Admin Phone: +1.6512971111 Admin Phone Ext:
Admin Fax: +1.6512975368
Admin Fax Ext:
Admin Email: nic<%>nic.state.mn.us
Admin Application Purpose: P5
Admin Nexus Category: C21
Registry Tech ID: C7705028-US
Tech Name: Network Operations Center
Tech Organization: State of Minnesota
Tech Street: Office of Enterprise Technology Tech Street: 500 Centennial Office Building Tech Street: 658 Cedar Street Tech City: St. Paul Tech State/Province: MN Tech Postal Code: 55155 Tech Country: US Tech Phone: +1.6512971111 Tech Phone Ext:
Tech Fax: +1.6512975368
Tech Fax Ext:
Tech Email: nic<%>nic.state.mn.us
Tech Application Purpose: P5
Tech Nexus Category: C21
Registry Domain Manager ID: C7704880-US
Domain Manager Name: Network Operations Center Domain Manager Organization: State of Minnesota Domain Manager Street: Office of Enterprise Technology Domain Manager Street: 500 Centennial Office Building Domain Manager Street: 658 Cedar Street Domain Manager City: St. Paul Domain Manager State/Province: MN Domain Manager Postal Code: 55155 Domain Manager Country: US Domain Manager Phone: +1.6512971111 Domain Manager Phone Ext:
Domain Manager Fax: +1.6512975368
Domain Manager Fax Ext:
Domain Manager Email: nic<%>nic.state.mn.us Domain Manager Application Purpose: P5 Domain Manager Nexus Category: C21 Name Server: ns3.state.mn.us Name Server: ns2.state.mn.us Name Server: ns1.state.mn.us
DNSSEC: signedDelegation
URL of the ICANN Whois Inaccuracy Complaint Form: https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.icann.org%2Fwicf%2F&amp;data=04%7C01%7Clee.knutson%40MINNSTATE.EDU%7C74faa8d0779d41a3ab7e08d8cb7516ea%7C5011c7c60ab446ab9ef4fae74a921a7f%7C0%7C0%7C637483051048592372%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=69TXpam1PL0rEw59mXagz4L2biZ671WpxzFw9uz3KS4%3D&amp;reserved=0
>>> Last update of WHOIS database: 2021-02-07T14:25:40Z