Alternately, we are more secure as a nation state because oil is a global market. Then, as countries become more reliant on each other for crude, revenue, and finished petroleum products they are less likely to upset the balance. Additionally, in 2012, we imported ~40% of our oil (lowest it's been in a long time), and our biggest import country, by far, is Canada. Here's an EIA link: http://www.eia.gov/tools/faqs/faq.cfm?id=727&t=6
Terrorism can be a problem of course, but I would be more concerned about the grid than our access to oil.
"countries become more reliant on each other for crude"
If the country that is selling you oil/energy is doing bad things this reliant nature of our relationship also ties our hands when it comes to calling them on their shit. See the Ukraine or pretty much any geo-political matter.
Isolationism isn't the only solution, but inter-dependance has it's own drawbacks.
Terrorism can be a problem of course, but I would be more concerned about the grid than our access to oil.