The closest I can find to a "guide" is the Wikipedia entry on Breastfeeding in Public. It has a comprehensive list of attitudes by country and continent that is a good head start for many places.
Picking a country at random, for China it states:
Breastfeeding in public in China has traditionally been a nonissue, and objection had been unheard of until 2010s. The recent few instances of objection are apparently an effect of magnification of the social media. The notion that breastfeeding in public is inappropriate, offensive, or otherwise objectionable, seems to have been introduced as a result of globalization.
In Shanghai, breastfeeding in public is considered embarrassing by some, but it is also accepted by many. There have been calls for the establishment of babycare facilities in public places.
Searching for more info
If the country you are considering is not listed, has little information to be found there or if you want to check further, I would google "breastfeeding [country]" or "breastfeeding attitudes [country]" or "breastfeeding in public [country]". Again for the example of China above and the last query I get first hit the above mentioned Wiki and then a set of recent articles, such as "China's breastfeeding mothers in cover up dilemma" which also gives a good impression on what seems the current attitude:
Debate in China over breastfeeding in public is not a new one and is one that mothers and the general public have struggled with for generations. Lately, the general attitude has shifted to demanding mothers not to breastfeed in public and to “respect privacy”.
Breastfeeding on planes
In the motherhood blog "PhD in Parenting" there is an interesting guide on breastfeeding policies of various airlines. It is of 2008 unfortunately and may not have been maintained since (the blog is no longer active as of 2015). As above, you could do a search such as "breastfeeding [name of airline]".
Again, doing an example search for Delta Airlines, the first link is a Delta homepage on Flying with Children where it says under "infant travel"
Delta fully supports a woman’s right to breast-feed on board Delta and Delta Connection aircraft and in Delta facilities. Breast pumps are allowed on board.
and that matches with the info in the blog.
Surveys and studies
If you like a more scientific take, there is a 2014 survey conducted in Brazil, China, France, Germany, Hungary, Mexico, Turkey, the United Kingdom and the United States on breastfeeding by Lansinoh (a company active in breastfeeding supplies, so be careful). All results can be accessed there or have a look to this article in "Mothermag".
There is also an article on "Breastfeeding in Public: A Global Review of Different Attitudes towards It" in the "Journal of Pediatrics & Neonatal Care". It comes to the little surprising conclusion that
Acceptance of public breastfeeding varies tremendously around the world. United States of America and some European countries accept and support breastfeeding in public both in theory and practise. These countries have recently established relevant legislation that protects breastfeeding in public places as well as at workplace. Since breast milk is critical for both maternal and child health, local, national and international public health organizations should consider promoting both legislative and marketing activities to promote acceptance of public nursing.
Word of warning: don't click the pdf link for that article, it wrongly links to another article that I assume you don't want to see!