Yes, you can marry someone with the same name as your sibling in America without changing your name legally first. There are no legal restrictions or requirements in the United States that prevent individuals with the same name from marrying each other. Marriage laws typically focus on factors such as age, consent, and familial relationships, but not on names.
While it might lead to some confusion within your family or among your friends, having the same name as your sibling's spouse does not pose any legal barriers to marriage in the United States. People with common names or shared names with relatives get married without any legal issues all the time.
Remember, when it comes to legal matters, it's always a good idea to consult with a legal professional to ensure you are aware of any specific laws or regulations that may apply to your situation.