The Four Reasons East Coasts Get Colder

Eastern North America and East Asia experience winters far colder than Europe or Western North America at the same latitude. Why is this? Is it due to the Gulf Stream/Kuroshio Current? Or the Rocky Mountains? Are there other factors at play?
Image sources:
Earth observatory.nasa.gov
earth.nullschool.net
Google Earth
Wikipedia Commons (sacratomato_hr, Chicoutimi, Karamanskaya, Jules Verne Times Two / julesvernex2.com / CC-BY-SA-4 julesvernex2.com, Korean Culture and Information Service (Jeon Han), Paul Gierszewski, Dennis Jarvis from Halifax, Canada, Gérald Tapp, Francesco Varenesi from Italy).
Flickr CC-BY-SA ( shizhao www.flickr.com...
江上清风1961 ,Ninara www.flickr.com...)
Information Sources:
Lows over the ocean influence the path of cold air (and Continental Polar Air masses):
Winter Cold of Eastern Continental Boundaries Induced by Warm Ocean Waters. Yohai Kaspi and Tapio Schneider in Nature, Vol. 471, pages 621-624; March 31, 2011.
Topographic effect on cold air mass movement:
Tibetan Plateau climate dynamics: recent research progress and outlook. National Science Review, Volume 2, Issue 1, March 2015, Pages 100-116. Guoxiong Wu, Anmin Duan, Yimin Liu, Jiangyu Mao, Rongcai Ren, Qing Bao, Bian He, Boqi Liu, Wenting Hu.
Iwasaki, T., T. Shoji, Y. Kanno, M. Sawada, M. Ujiie, K. Takaya, and M. Ujie, 2014: Isentropic analysis of polar cold airmass streams in the Northern Hemispheric winter. J. Atmos. Sci., 71, 2230-2243
Kanno, Y., M. R. Abdillah, and T. Iwasaki, 2015: Charge and discharge of polar cold air mass in Northern Hemispheric winter. Geophys. Res. Lett., 42, 7187-7193
Hui Xiaoying, Luo Siwei. THE NUMERICAL EXPERIMENTS OF OROGRAPHIC INFLUENCE ON TWO COLD-OUTBURSTS[J]. Plateau Meteorology, 1993, 12(3): 283-293.
The importance of the Gulf Stream:
Is the Oceanic Heat Transport in the North Atlantic Irrelevant to the Climate in Europe? P. B. Rhines, University of Washington, Seattle USA S. Häkkinen, NASA Goddard Space Flight Center, Greenbelt USA
citeseerx.ist.p...
East Coast Cold Currents:
Petrie, B., and A. Isenor, 1985: The near-surface circulation and exchange in the Newfoundland Grand Banks region, Atmosphere-Ocean, 23(3), 209-227.
Reynaud, T.H., A.J. Weaver, and R.J. Greatbatch, 1995: Summer mean circulation of the Northwestern Atlantic Ocean, Journal of Geophysical Research, 100, 779-816.
Smith, E.H., F.M. Soule, and O. Mosby, 1937: The Marion and General Green expeditions to Davis Strait and the Labrador Sea, Bull. U.S. Coast Guard, 19, 259 pp.
City Climate Data: NOAA, World Meteorological Organization, China Meteorological Administration, Meteo France, Environment Canada, Instituto Português do Mar e da Atmosfera, Korea Meteorological Administration, Weather Atlas.
San Francisco History of Record Lows: www.currentres...