Obviously it spread at different rates, depending on the developmental levels of individual nations. I've got some information together on Russia, with the help of reviews of a book by Jonathan Coopersmith. The book is called, The Electrification of Russia, 1880-1926, and despite being unable to find a copy of it, it sounds like it was custom written for this question.
The Russian state under the Tsars seems to have been quite unreceptive towards new technologies. Russian inventors found their fame in Western Europe, receiving no appreciation in Russia. The obstacles to electrification were many. Infrastructure wasn't available, and local government authorities weren't willing to pay for it, seeing as they were already in debt. There were political disputes too, both local and national, all contributing to delays.
The Russian military was the leader in the adoption of electricity, so it wasn't unheard of in Russia. As well as this, while its uptake in the civilian world was slow, it wasn't non-existent. This suggests it was available in modest amounts, most likely in the homes of the rich. With pure speculation, I'd suggest it was also more likely to be found in the homes of those who had travelled outside of Russia, and had seen its application elsewhere. Diplomats would be well aware of the uses of electricity by these groups, and spending time abroad, by its application there.
But America was not fully electrified either. In 1907 only 8% of American homes had electricity. This grew to 35% in 1920, and 70% in 1930. The reason for this was because the technology for carrying large amounts of electricity over distance had not yet been completely worked out.
Knowing this, it's reasonable to say that Russian diplomats would most likely be surprised at the way electricity was deployed in American homes. However, I don't think it was as widespread as you seem to think it was. With this in mind, it's more likely any surprise was rooted in the application of domestic use, rather than the actual concept of electricity.
Electricity in Japan "appeared" in 1878 and began to spread to the general population in 1887.
Here's a source for that : History of Japan's Electric Power Industry
I don't have my books on me and I'm writing with my phone so I can't give a detailed enough answer, but I'll make sure to edit this message once I'll be at home.
Edit :
At first I'd like to add some historical context. During more than 200 years, Japan was isolated (aside from some trading posts) by the will of the Tokugawa Shogunate, it is the « sakoku ». In 1853, the « black ships » of the commodore Matthew Perry ended by force the sakoku and opened Japan to the European traders and, through the traders, to technology.
Does it mean that during the sakoku Western technology was unheard of in Japan ? Not really, the elite and the ruling class had some knowledge of Western philosophy and technology, that was called 蘭学 (rangaku, Dutch studies), because it was brought by Dutch merchants.
To go back to 1853, the commodore Perry ended the sakoku. That showed one thing to the Japanese people : The Tokugawa Shogunate was weak. Besides, more and more foreigners arrived in Japan, with all their money, their weapons, their technology … And were considered a sort of colonial invaders because they dictated their will to the Tokugawa. Of course the people began to doubt the Tokugawa really wanted what's best for Japan. That led to a movement called 尊王攘夷 (sonnô jôi, revere the Emperor, expell the Barbarians) that wanted to get rid of the foreigners and make the Emperor of Japan (who had, during the Shogunate, nothing but a ceremonial rôle) the actual ruler of Japan. Long story short, in 1868 the factions supporting the Emperor won and it was the beginning of Meiji era, ruled by Emperor Meiji, who wanted to modernize Japan and make it a strong industrialized nation.
It took about 30 years for Japan to go from a feodal system (the Tokugawa Shogunate) to a modern European-like prosperous nation-state. How did the Meiji government do ? They sent Japanese nationals to the West with the mission to study the European ways and technologies, and accepted foreigners (in the end, even if the Emperor of Japan used the sonnô jôi movement to retake power, they never expelled the « barbarians », instead they replaced it with a new motto : 富国強兵 fukoku kyôhei : rich country strong army) from the West so they could bring their technology with them, explain new military tactics to the Japanese army, … Basically teach everything that could make Japan an industrialized nation. That answers to a part of the initial question : How fast could technological progress be spread ? Very fast provided the government had a good technological policy.
Now electricity … Electricity is an interesting subject because Japan is a country that adopted and found use for electricity very quickly.
Tokyo Electric Lighting (I will abridge it TEL, but you can also find it called : Tokyo Electric Power, Tokyo Electric Lighting Company, and other similar names), an ancestor of modern day TEPCO, has been founded in 1883, began to work over power plants in 1886 and in November 1887 they had finished building their second electric light station that produced electricity available to their custumors. The high profit generated by TEL encouraged Japanese businessmen to create their own local Electric Company, such as Nagoya Electric Company launched in 1887.
The main use of electricity was lighting. In 1890 there were about 20000 electric lamps in Japan. In 1896, there were 100 000 electric lamps throughout Japan, and a bit more than 10 000 households received electricity.
When it comes to electric generation capacities, in 1903, 50 000 kW (not sure, some sources state it was closer to 45 000 kW) was generated in Japan : 50 % by electric companies, and the rest by plants operated by the governments or attached to companies that wanted their « own » electricity without depending on electric companies.
So, to answer the question, no, Japanese ambassadors would not have been impressed by electricity in America, they would even consider themselves quite « advanced » compared to the other nations.
My sources for this explanation :
Electricity was being used in South Africa by the mining industry as early as the 1880s. Prior to 1990 less than a third of South Africans had access to electricity, which had increased to 76% of households by 2014.
http://www.gsb.uct.ac.za/files/SAElectrificationworkingpaperfinal.pdf http://www.ee.co.za/article/toward-universal-energy-access-designing-new-household-electrification-strategy-sa.html http://heritage.eskom.co.za/heritage/electricity_in_south_africa.htm