Final answer:
Some Americans opposed U.S. expansion due to concerns about the lack of constitutional protections, the United States' military strength, and the potential impact on overproduction.
Step-by-step explanation:
There were several reasons why some Americans opposed U.S. expansion in the 1800s. One reason was that they believed the newly acquired territories did not receive the same constitutional protections as the existing states. They were concerned about the rights and freedoms of the people living in these territories.
Another reason for opposition was the fear that the United States lacked the military strength to successfully expand. Some believed that engaging in overseas expansion would stretch the military too thin and leave the nation vulnerable to attacks.
Finally, some critics argued that expansion would not solve the problem of overproduction. They believed that expanding the territory would only lead to more land being cultivated and more goods being produced, exacerbating the existing economic challenges.