Steve M

Whether a speeding ticket is a crime, infraction, or something else varies dramatically by state. Here in Texas, I don't think we have such a notion of an "infraction." What would be called an infraction in California (most moving violations) are Class C misdemeanors. So, although officially a "crime," most of the time when asked about criminal history, a form will say "except traffic violations" anyway.

Whether a misdemeanor, infraction, or something else, an unpaid speeding ticket is not felony. Only felony warrants are enforceable across state borders. So, there's no worries about running into trouble with state or local authorities in any state except Texas. In Texas, however, my expectation is that if you have any interaction with law enforcement that causes them to run your record, that you'll quickly find you have an outstanding warrant and you'll be arrested and taken to jail, where you'll stay until you pay the outstanding fine.

As to whether US Immigration will know or care about an unpaid speeding ticket, I have no idea. In my opinion, they certainly should. I find it offensive that you'd come here as a guest to our country, violate the law, ignore the ticket, then expect to be let back in in the future. Visiting any country other than your own is a privilege, not a right. I think US immigration authorities should deny entry to non-citizens that have outstanding tickets.