"Bound" is correct in in the past tense. "Bind" is right in the present tense.
Bind is an active verb meaning to tie together. That is exactly what the interstate highway system does: it ties together the people and the settlements of the country.
Stick means to attach one thing to another, often with glue. You can stick a note on a bulletin board. Your phrase, stick together, is reflexive and usually refers to people. People who have chosen to adhere to one another and form a group "stick together."
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