Here is a paper on the gentic diversity of burms in the ENP
Collins, T. M., Freeman, B., & Snow, S. (2008). Final report: genetic characterization of populations of the nonindigenous Burmese python in Everglades National Park. Final report for the South Florida Water Management District. Department of Biological Sciences, Florida International University, Miami, Florida.
link to this article:
http://reptile-nation.com/wp-content/uploads/2012/05/FloridaBurmGenetics.pdf
Right there in the abstract it states, "Multiple analyses including assignment methods and F- statistics revealed that the ENP Burmese pythons are genetically distinct from pythons sampled from Vietnam, but display little genetic differentiation within the Park, with the exception of a few outliers. The lack of genetic differentiation of most Burmese Pythons in ENP may indicate either a panmictic freely interbreeding population in the Park, or alternatively, limited genetic variation in the captive- bred populations that are the likely source of these snakes. Sampling of mothers and offspring provided no evidence of parthenogenetic reproduction in ENP pythons."
Current distribution map:
Reports on these snakes surviving outside of South FL:
"Here we show that a predicted continental expansion is unlikely based on the ecology of the organism and the climate of the U.S."
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002931
Pyron, R. A., Burbrink, F. T., & Guiher, T. J. (2008). Claims of potential expansion throughout the US by invasive python species are contradicted by ecological niche models. PloS one, 3(8), e2931.
"Only one of 10 telemetered pythons survived the cold snap, whereas 59 of 99 (60%) non-telemetered pythons for which we determined fate survived." in regards to pythons in South FL where they are reported to be thriving.
http://link.springer.com/article/10.1007/s10530-010-9797-5
Mazzotti, F. J., Cherkiss, M. S., Hart, K. M., Snow, R. W., Rochford, M. R., Dorcas, M. E., & Reed, R. N. (2011). Cold-induced mortality of invasive Burmese pythons in south Florida. Biological Invasions, 13(1), 143-151.
