Usefulness of attending a Thai temple in the United States
Sorry not Thai.

I'm a westerner (black American) who attends a Thai Forest temple, and they were welcoming to me since the beginning. Honestly as someone who has been attending for a while, the "Sunday service" question would have been strange to me too. We have chanting and meditation open to laypeople once in the morning and evening. Of course, visitors are welcome all day, and there are regulars who also make lunch for the monks, and offer other food, medicine, and other donations.

It is not good to make decisions based on your imagination. For example, your assessment would be incorrect if applied to our temple. Offering robes formerly is mostly only done once a year for Vesaka. Also, donations, chanting, and meditation go hand-in-hand. Offering food, taking refuge, praising the Three Jewels, practicing gratitude for things we do not normally think about (food, shelter, clothing), and spreading loving-kindness is the basis for a healthy meditative life. At my temple, they speak both Thai and English, and if you can find an English version of the Pali chanting book they use (technically their books are already in "English" as far as using transliterated Roman script), it is easy to pick up on the keywords that let you know what you are chanting at any given moment. 

Also, the Buddhists in our temple are comfortable with going to Mahayana-based temples as well, and "doing as the Romans do", which includes more incense offering and devotional aspects like that.

Saying that, the Dhammakyut orders formed from a movement that basically Protestantized Buddhism in that region, so you have to take in account how Thai Buddhism is practiced in modern times when considering practicing Thai Buddhism.

It is really like any other new place. You just go in and check it out, without expectations, meet it on its own terms, then decide whether the temple is for you or not.