Once your brand starts selling in the USA, a trademark is cheap insurance. If someone else registers it first, winning it back is expensive.
In Europe, registration grants the rights; in the USA, actual use also counts, but in a dispute the winner is almost always the party holding a federal registration with the USPTO. If your product gains market recognition without a registration, you are systematically tempting fate.
The worst-case scenario is familiar to many: a distributor or competitor registers your name themselves and later sells it back to you.
A USPTO application carries a government filing fee of a few hundred dollars per class, and with an attorney it usually comes to between 1,000 and 2,000 dollars. A foreign applicant must use a US-licensed attorney; this is mandatory. The proceeding takes 8 to 14 months, but protection is counted from the moment the application is filed.
If you hold an EU trademark, you can expand more cheaply and easily through the Madrid System.
A private-label manufacturer is in no hurry: your name does not travel with the goods. A seller with their own brand should act when the first US deals are tangible, not still just a dream. Register before the big marketing push, not after.
The first consultation is free: together we'll see who in the US already buys your product and how to reach them.