They don't want the country to fall apart, they want rights for immigrants and are trying to show the nation that they are an essential part of the US.

There are only 11-12 million working immigrants in this country. The only way for them to get attention is to march together, cause some traffic so people take notice, and boycott for a day. Cities like Chicago, New York, Los Angeles, San Diego etc. will feel the effects.

I wouldn't expect Huntsville and Orlando to be affected.