When Samantha asks Andrew about his son he states that he will be 6 yrs old tomorrow when his birthday is actually that very day because the night before he called his son to wish him a happy birthday and he said he was calling then because he wouldn't be able to call tomorrow.
The Pre-Columbian pyramid the two protagonists climb is located in a jungle setting. From the top of this pyramid they are able to view the border between Texas and Mexico, which is nowhere near any jungle.
The scene where Samantha is about to board the ferry is located in Cancun on the southern part of Mexico but the map showing the infected zone is close to the border with the United States on the north.
At the start of the film, in "San Jose, Central America" we see a sign showing "US Border 200km". The shortest distance between the Central American border (Mexico/Guatemala) and the US Border is approximately 1,700km.
A cephalopod mollusk (or even a vertebrate animal) of that giant size would have no ability to walk or move on land. It would be crushed by it's own massive weight. Since the creature is of extraterrestrial origin, however, its alien anatomy might have certain adaptations that allow it to walk on land without being crushed by its own weight.
When the two characters arrive at the deserted town on the US side of the border, and the camera pans the town and focuses on the evacuation side, you can see a pickup truck driving down the road. (This is likely the result of using open sets for filming, which allowed for the shooting areas local population to be accidentally captured in a shot.)