Yes and no. The coasts, especially New York, legitimately have a lot of melting pot action going on. The border states do too. New York is probably the most diverse city in the world by ethnic composition. But most of the Americas have or at least had a lot of immigration. Toronto is another huge immigrant city. Canada, Argentina, and Brazil have all seen their fair share of diverse waves of immigration.
One thing that may be lost on Anglo-Americans is the diversity of “Latin America.” It’s predominantly Spanish speaking, but also includes Portuguese and French. The indigenous tribes left a stronger legacy in many of those countries than they did in the USA, and there are many differences both within and between them – with strong African influences too.